U.S. patent application number 17/502190 was filed with the patent office on 2022-05-19 for battery and method of manufacturing same.
This patent application is currently assigned to PRIME PLANET ENERGY & SOLUTIONS, INC.. The applicant listed for this patent is PRIME PLANET ENERGY & SOLUTIONS, INC.. Invention is credited to Toshiki IMABORI, Yohei MUROYA, Kohji UMEMURA.
Application Number | 20220158311 17/502190 |
Document ID | / |
Family ID | 1000005961676 |
Filed Date | 2022-05-19 |
United States Patent
Application |
20220158311 |
Kind Code |
A1 |
MUROYA; Yohei ; et
al. |
May 19, 2022 |
BATTERY AND METHOD OF MANUFACTURING SAME
Abstract
A battery includes: a conductive member provided with a through
hole; and a terminal member inserted in the through hole and having
a tip portion exposed on the conductive member. A joined portion of
the tip portion of the terminal member to the conductive member is
formed. The joined portion includes a thick portion at which a
thickness of the terminal member is relatively thick, and a thin
portion at which the thickness of the terminal member is relatively
thin.
Inventors: |
MUROYA; Yohei;
(Kakogawa-shi, JP) ; UMEMURA; Kohji; (Ono-shi,
JP) ; IMABORI; Toshiki; (Kasai-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PRIME PLANET ENERGY & SOLUTIONS, INC. |
Tokyo |
|
JP |
|
|
Assignee: |
PRIME PLANET ENERGY &
SOLUTIONS, INC.
Tokyo
JP
|
Family ID: |
1000005961676 |
Appl. No.: |
17/502190 |
Filed: |
October 15, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 50/533 20210101;
H01M 50/103 20210101; H01M 50/564 20210101; H01M 50/176 20210101;
H01M 50/528 20210101; H01M 50/553 20210101 |
International
Class: |
H01M 50/533 20060101
H01M050/533; H01M 50/553 20060101 H01M050/553; H01M 50/564 20060101
H01M050/564; H01M 50/528 20060101 H01M050/528; H01M 50/103 20060101
H01M050/103; H01M 50/176 20060101 H01M050/176 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 16, 2020 |
JP |
2020-190260 |
Claims
1. A battery comprising: a conductive member provided with a
through hole; and a terminal member inserted in the through hole
and having a tip portion exposed on the conductive member, wherein
a joined portion of the tip portion of the terminal member to the
conductive member is formed, and the joined portion includes a
thick portion at which a thickness of the terminal member is a
relatively thick, and a thin portion at which the thickness of the
terminal member is relatively thin.
2. The battery according to claim 1, wherein the thin portion
extends in a radial direction of the joined portion.
3. The battery according to claim 1, wherein the battery has an
upper surface having a quadrangular shape, the upper surface
including a long side direction and a short side direction, and a
plurality of the thick portions are formed to be separated from
each other in the short side direction.
4. The battery according to claim 1, wherein the battery has an
upper surface having a quadrangular shape, the upper surface
including a long side direction and a short side direction, and the
thick portion has a portion having a maximum thickness on a central
axis of the joined portion, the central axis extending in the short
side direction.
5. The battery according to claim 1, wherein the thin portion
extends radially.
6. The battery according to claim 1, wherein the thick portion and
the thin portion are alternately disposed in a circumferential
direction of the joined portion.
7. The battery according to claim 1, wherein the joined portion is
formed to have a thickness that is gradually decreased in a
direction from the thick portion toward the thin portion.
8. The battery according to claim 1, wherein an outer circumference
of the joined portion is provided with a recess recessed toward a
center of the joined portion at a portion at which the thin portion
is located.
9. The battery according to claim 1, wherein the joined portion is
formed by a swaged portion of the tip portion of the terminal
member to the conductive member.
10. The battery according to claim 9, wherein the swaged portion
has a planar shape including a pair of straight portions and a pair
of curved portions, and the thin portion is located between each of
the straight portions and each of the curved portions.
11. The battery according to claim 1, further comprising an
electrode assembly, wherein the conductive member is a current
collector that electrically connects the electrode assembly and the
terminal member to each other.
12. A method of manufacturing a battery, the method comprising:
inserting a terminal member into a through hole of a conductive
member; forming a joined portion that has a central axis extending
in a short side direction of an upper surface of the battery, the
joined portion being a portion at which a tip portion of the
terminal member is joined to the conductive member; and processing
the joined portion to form a thick portion on the central axis, the
thick portion being a portion at which a thickness of the joined
portion is relatively thick.
13. The method of manufacturing the battery according to claim 12,
wherein the processing of the joined portion is performed
simultaneously with the joining of the tip portion of the terminal
member to the conductive member by swaging.
14. The method of manufacturing the battery according to claim 12,
wherein the processing of the joined portion is performed after the
joining of the tip portion of the terminal member to the conductive
member.
15. The method of manufacturing the battery according to claim 12,
wherein a thin portion at which a thickness of the joined portion
is relatively thin is formed at a position adjacent to the thick
portion in a circumferential direction of the joined portion.
Description
[0001] This nonprovisional application is based on Japanese Patent
Application No. 2020-190260 filed on Nov. 16, 2020, with the Japan
Patent Office, the entire contents of which are hereby incorporated
by reference.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The present disclosure relates to a battery and a method of
manufacturing the battery.
Description of the Background Art
[0003] Conventionally, in a battery, a terminal member and a
current collector have been joined to each other by swaging. Such a
structure is disclosed, for example, in Japanese Patent Laying-Open
No. 2011-076867 (PTL 1).
[0004] In PTL 1, a secondary battery having a low resistance can be
provided by using both fixation by swaging and laser welding in
fixation between a current collector and a terminal member.
[0005] However, when the thickness of the swaged portion is
insufficient, joining strength of the terminal member may be
decreased, disadvantageously. On the other hand, provision of an
excessively increased thickness to an unnecessary portion in the
joined portion unfavorably leads to over-engineering.
SUMMARY OF THE INVENTION
[0006] An object of the present disclosure is to provide: a battery
in which joining strength of a terminal member can be improved
while avoiding over-engineering; and a method of manufacturing such
a battery.
[0007] A battery according to the present disclosure includes: a
conductive member provided with a through hole; and a terminal
member inserted in the through hole and having a tip portion
exposed on the conductive member. A joined portion of the tip
portion of the terminal member to the conductive member is formed.
The joined portion includes a thick portion at which a thickness of
the terminal member is relatively thick, and a thin portion at
which the thickness of the terminal member is relatively thin.
[0008] A method of manufacturing a battery according to the present
disclosure includes: inserting a terminal member into a through
hole of a conductive member; forming a joined portion that has a
central axis extending in a short side direction of an upper
surface of the battery, the joined portion being a portion at which
a tip portion of the terminal member is joined to the conductive
member; and processing the joined portion to form a thick portion
on the central axis, the thick portion being a portion at which a
thickness of the joined portion is relatively thick.
[0009] The foregoing and other objects, features, aspects and
advantages of the present invention will become more apparent from
the following detailed description of the present invention when
taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a perspective view of a prismatic secondary
battery.
[0011] FIG. 2 is a cross sectional view taken along II-II in FIG.
1.
[0012] FIG. 3 is a plan view of a positive electrode plate included
in an electrode assembly.
[0013] FIG. 4 is a plan view of a negative electrode plate included
in the electrode assembly.
[0014] FIG. 5 is a plan view showing the electrode assembly
including the positive electrode plate and the negative electrode
plate.
[0015] FIG. 6 is a diagram showing a structure of connection
between the electrode assembly and each of a positive electrode
current collecting member and a negative electrode current
collecting member.
[0016] FIG. 7 is a diagram showing a structure of attaching of the
positive electrode current collecting member and the negative
electrode current collecting member on a sealing plate.
[0017] FIG. 8 is a cross sectional view taken along VIII-VIII in
FIG. 7.
[0018] FIG. 9 is a cross sectional view taken along IX-IX in FIG.
7.
[0019] FIG. 10 is a diagram showing a state in which the sealing
plate and the electrode assembly are connected to each other.
[0020] FIG. 11 is a diagram showing an arrangement of bus bars in a
battery pack.
[0021] FIG. 12 is a diagram showing an electrode terminal and a
current collector before joining by swaging.
[0022] FIG. 13 is a diagram showing the electrode terminal and the
current collector after the joining by swaging.
[0023] FIG. 14 is a diagram showing a first exemplary shape of a
swaged portion.
[0024] FIG. 15 is a diagram showing a second exemplary shape of the
swaged portion.
[0025] FIG. 16 is a diagram showing a third exemplary shape of the
swaged portion.
[0026] FIG. 17 is a diagram showing a fourth exemplary shape of the
swaged portion.
[0027] FIG. 18 is a diagram showing a fifth exemplary shape of the
swaged portion.
[0028] FIG. 19 is a diagram showing a structure of a swaged portion
outside the battery case.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] Hereinafter, embodiments of the present disclosure will be
described. It should be noted that the same or corresponding
portions are denoted by the same reference characters, and may not
be described repeatedly.
[0030] It should be noted that in the embodiments described below,
when reference is made to number, amount, and the like, the scope
of the present disclosure is not necessarily limited to the number,
amount, and the like unless otherwise stated particularly. Further,
in the embodiments described below, each component is not
necessarily essential to the present disclosure unless otherwise
stated particularly.
[0031] (Configuration of Prismatic Secondary Battery 1)
[0032] FIG. 1 is a perspective view of a prismatic secondary
battery 1. FIG. 2 is a cross sectional view taken along II-II in
FIG. 1.
[0033] As shown in FIGS. 1 and 2, prismatic secondary battery 1
includes a battery case 100, an electrode assembly 200, an
insulating sheet 300, a positive electrode terminal 400, a negative
electrode terminal 500, a positive electrode current collecting
member 600, a negative electrode current collecting member 700, and
a cover member 800.
[0034] Battery case 100 is constituted of: a prismatic exterior
body 110 that is provided with an opening and that has a prismatic
tubular shape having a bottom; and a sealing plate 120 that seals
the opening of prismatic exterior body 110. Each of prismatic
exterior body 110 and sealing plate 120 is preferably composed of a
metal, and is preferably composed of aluminum or an aluminum
alloy.
[0035] Sealing plate 120 is provided with an electrolyte solution
injection hole 121. After injecting an electrolyte solution into
battery case 100 via electrolyte solution injection hole 121,
electrolyte solution injection hole 121 is sealed by a sealing
member 122. As sealing member 122, for example, a blind rivet or
another metal member can be used.
[0036] Sealing plate 120 is provided with a gas discharge valve
123. Gas discharge valve 123 is fractured when pressure in battery
case 100 becomes more than or equal to a predetermined value. Thus,
gas in battery case 100 is discharged to outside of battery case
100.
[0037] Electrode assembly 200 is accommodated in battery case 100
together with the electrolyte solution. Electrode assembly 200 is
formed by stacking positive electrode plates and negative electrode
plates with separators being interposed therebetween. Insulating
sheet 300, which is composed of a resin, is disposed between
electrode assembly 200 and prismatic exterior body 110.
[0038] A positive electrode tab 210A and a negative electrode tab
210B are provided at an end portion of electrode assembly 200 on
the sealing plate 120 side.
[0039] Positive electrode tab 210A and positive electrode terminal
400 are electrically connected to each other via positive electrode
current collecting member 600. Positive electrode current
collecting member 600 includes a first positive electrode current
collector 610 and a second positive electrode current collector
620. It should be noted that positive electrode current collecting
member 600 may be constituted of one component. Positive electrode
current collecting member 600 is preferably composed of a metal,
and is more preferably composed of aluminum or an aluminum
alloy.
[0040] Negative electrode tab 210B and negative electrode terminal
500 are electrically connected to each other via negative electrode
current collecting member 700. Negative electrode current
collecting member 700 includes a first negative electrode current
collector 710 and a second negative electrode current collector
720. It should be noted that negative electrode current collecting
member 700 may be constituted of one component. Negative electrode
current collecting member 700 is preferably composed of a metal,
and is more preferably composed of copper or a copper alloy.
[0041] Positive electrode terminal 400 is fixed to sealing plate
120 with an outer side insulating member 410 being interposed
therebetween, outer side insulating member 410 being composed of a
resin. Negative electrode terminal 500 is fixed to sealing plate
120 with an outer side insulating member 510 being interposed
therebetween, outer side insulating member 510 being composed of a
resin.
[0042] Positive electrode terminal 400 is preferably composed of a
metal, and is more preferably composed of aluminum or an aluminum
alloy. Negative electrode terminal 500 is preferably composed of a
metal, and is more preferably composed of copper or a copper alloy.
Negative electrode terminal 500 may have: a region that is composed
of copper or a copper alloy and that is disposed on the inner side
of battery case 100; and a region that is composed of aluminum or
an aluminum alloy and that is disposed on the outer side of battery
case 100.
[0043] Cover member 800 is located between first positive electrode
current collector 610 and electrode assembly 200. Cover member 800
may be provided on the negative electrode current collector side.
Further, cover member 800 is not an essential member, and may be
omitted as appropriate.
[0044] (Configuration of Electrode Assembly 200)
[0045] FIG. 3 is a plan view of positive electrode plate 200A
included in electrode assembly 200. Positive electrode plate 200A
has a main body 220A in which a positive electrode active material
composite layer is formed on each of both surfaces of a positive
electrode core body constituted of an aluminum foil having a
quadrangular shape, the positive electrode active material
composite layer including a positive electrode active material (for
example, lithium nickel cobalt manganese composite oxide or the
like), a binder (polyvinylidene difluoride (PVdF) or the like), and
a conductive material (for example, a carbon material or the like).
The positive electrode core body protrudes from an end side of the
main body portion, and the positive electrode core body thus
protruding constitutes positive electrode tab 210A. A positive
electrode protection layer 230A including alumina particles, a
binder, and a conductive material is provided on positive electrode
tab 210A at a portion adjacent to main body 220A. Positive
electrode protection layer 230A has an electric resistance larger
than that of the positive electrode active material composite
layer. The positive electrode active material composite layer may
include no conductive material. Positive electrode protection layer
230A may not be necessarily provided.
[0046] FIG. 4 is a plan view of negative electrode plate 200B
included in electrode assembly 200. Negative electrode plate 200B
has a main body 220B in which a negative electrode active material
layer is formed on each of both surfaces of a negative electrode
core body constituted of a copper foil having a quadrangular shape.
The negative electrode core body protrudes from an end side of main
body 220B, and the negative electrode core body thus protruding
constitutes negative electrode tab 210B.
[0047] FIG. 5 is a plan view showing electrode assembly 200
including positive electrode plates 200A and negative electrode
plates 200B. As shown in FIG. 5, electrode assembly 200 is produced
such that positive electrode tabs 210A of positive electrode plates
200A are stacked and negative electrode tabs 210B of negative
electrode plates 200B are stacked at one end portion of electrode
assembly 200. For example, about 50 positive electrode plates 200A
and about 50 negative electrode plates 200B are stacked. Positive
electrode plates 200A and negative electrode plates 200B are
alternately stacked with separators being interposed therebetween,
each of the separators being composed of polyolefin, each of the
separators having a quadrangular shape. It should be noted that a
long separator may be used with the separator being folded in a
meandering manner.
[0048] (Structure of Connection Between Electrode Assembly 200 and
Each of Positive Electrode Current Collecting Member 600 and
Negative Electrode Current Collecting Member 700)
[0049] FIG. 6 is a diagram showing a structure of connection
between electrode assembly 200 and each of positive electrode
current collecting member 600 and negative electrode current
collecting member 700. As shown in FIG. 6, electrode assembly 200
includes a first electrode assembly element 201 (first stack group)
and a second electrode assembly element 202 (second stack group).
Separators are also disposed on the respective outer surfaces of
first electrode assembly element 201 and second electrode assembly
element 202. First electrode assembly element 201 and second
electrode assembly element 202 can be fixed in a stacked state by a
tape or the like, for example. Alternatively, an adhesive layer may
be provided on each of positive electrode plates 200A, negative
electrode plates 200B, and the separators to adhere the separators
and positive electrode plates 200A and to adhere the separators and
negative electrode plates 200B.
[0050] The plurality of positive electrode tabs 210A of first
electrode assembly element 201 constitute a first positive
electrode tab group 211A. The plurality of negative electrode tabs
210B of first electrode assembly element 201 constitute a first
negative electrode tab group 211B. The plurality of positive
electrode tabs 210A of second electrode assembly element 202
constitute a second positive electrode tab group 212A. The
plurality of negative electrode tabs 210B of second electrode
assembly element 202 constitute a second negative electrode tab
group 212B.
[0051] Second positive electrode current collector 620 and second
negative electrode current collector 720 are disposed between first
electrode assembly element 201 and second electrode assembly
element 202. Second positive electrode current collector 620 is
provided with a first opening 620A and a second opening 620B. First
positive electrode tab group 211A and second positive electrode tab
group 212A are connected onto second positive electrode current
collector 620 by welding, thereby forming welded connection
portions 213. First negative electrode tab group 211B and second
negative electrode tab group 212B are connected onto second
negative electrode current collector 720 by welding, thereby
forming welded connection portions 213. Welded connection portions
213 can be formed by, for example, ultrasonic welding, resistance
welding, laser welding, or the like.
[0052] (Structure of Attaching of Positive Electrode Current
Collecting Member 600 and Negative Electrode Current Collecting
Member 700 on Sealing Plate 120)
[0053] FIG. 7 is a diagram showing a structure of attaching of
positive electrode current collecting member 600 and negative
electrode current collecting member 700 on sealing plate 120. FIG.
8 shows a cross section taken along VIII-VIII in FIG. 7. FIG. 9
shows a cross section taken along IX-IX in FIG. 7.
[0054] First, the following describes attaching of positive
electrode current collecting member 600 on sealing plate 120 with
reference to FIGS. 7 and 8.
[0055] Outer side insulating member 410 composed of a resin is
disposed on the outer surface side of sealing plate 120. First
positive electrode current collector 610 and insulating member 630
(positive electrode current collector holder) composed of a resin
are disposed on the inner surface side of sealing plate 120. Next,
positive electrode terminal 400 is inserted into a through hole of
outer side insulating member 410, a positive electrode terminal
attachment hole of sealing plate 120, a through hole of first
positive electrode current collector 610, and a through hole of
insulating member 630. A swaged portion 400A located at the tip of
positive electrode terminal 400 is connected onto first positive
electrode current collector 610 by swaging. Thus, positive
electrode terminal 400, outer side insulating member 410, sealing
plate 120, first positive electrode current collector 610, and
insulating member 630 are fixed. It should be noted that the
portions of positive electrode terminal 400 and first positive
electrode current collector 610 connected to each other by the
swaging are preferably welded by laser welding or the like. It
should be noted that first positive electrode current collector 610
is provided with a countersunk hole 610A, and swaged portion 400A
is provided in countersunk hole 610A.
[0056] Further, second positive electrode current collector 620 is
disposed on insulating member 630 such that a portion of second
positive electrode current collector 620 overlaps with first
positive electrode current collector 610. In first opening 620A
provided in second positive electrode current collector 620, second
positive electrode current collector 620 is welded to first
positive electrode current collector 610 by laser welding or the
like.
[0057] As shown in FIG. 8, insulating member 630 has a tubular
portion 630A that protrudes on the electrode assembly 200 side.
Tubular portion 630A extends through second opening 620B of second
positive electrode current collector 620 and defines a hole portion
630B that communicates with electrolyte solution injection hole
121.
[0058] When attaching positive electrode current collecting member
600 on sealing plate 120, first positive electrode current
collector 610 is first connected to insulating member 630 on
sealing plate 120. Then, second positive electrode current
collector 620 connected to electrode assembly 200 is attached to
first positive electrode current collector 610. On this occasion,
second positive electrode current collector 620 is disposed on
insulating member 630 such that a portion of second positive
electrode current collector 620 overlaps with first positive
electrode current collector 610. Then, the circumference around
first opening 620A provided in second positive electrode current
collector 620 is welded to first positive electrode current
collector 610 by laser welding or the like.
[0059] Next, the following describes attaching of negative
electrode current collecting member 700 on sealing plate 120 with
reference to FIGS. 7 and 9.
[0060] Outer side insulating member 510 composed of a resin is
disposed on the outer surface side of sealing plate 120. First
negative electrode current collector 710 and insulating member 730
(negative electrode current collector holder) composed of a resin
are disposed on the inner surface side of sealing plate 120. Next,
negative electrode terminal 500 is inserted into a through hole of
outer side insulating member 510, a negative electrode terminal
attachment hole of sealing plate 120, a through hole of first
negative electrode current collector 710, and a through hole of
insulating member 730. A swaged portion 500A located at the tip of
negative electrode terminal 500 is connected onto first negative
electrode current collector 710 by swaging. Thus, negative
electrode terminal 500, outer side insulating member 510, sealing
plate 120, first negative electrode current collector 710, and
insulating member 730 are fixed. It should be noted that the
portions of negative electrode terminal 500 and first negative
electrode current collector 710 connected to each other by the
swaging are preferably welded by laser welding or the like.
[0061] Further, second negative electrode current collector 720 is
disposed on insulating member 730 such that a portion of second
negative electrode current collector 720 overlaps with first
negative electrode current collector 710. In first opening 720A
provided in second negative electrode current collector 720, second
negative electrode current collector 720 is welded to first
negative electrode current collector 710 by laser welding or the
like.
[0062] When attaching negative electrode current collecting member
700 on sealing plate 120, first negative electrode current
collector 710 is first connected to insulating member 730 on
sealing plate 120. Then, second negative electrode current
collector 720 connected to electrode assembly 200 is attached to
first negative electrode current collector 710. On this occasion,
second negative electrode current collector 720 is disposed on
insulating member 730 such that a portion of second negative
electrode current collector 720 overlaps with first negative
electrode current collector 710. Then, the circumference around
first opening 720A provided in second negative electrode current
collector 720 is welded to first negative electrode current
collector 710 by laser welding or the like.
[0063] (Structure of Connection Between Sealing Plate 120 and
Electrode Assembly 200)
[0064] FIG. 10 is a diagram showing a state in which sealing plate
120 and electrode assembly 200 are connected to each other. As
described above, first electrode assembly element 201 and second
electrode assembly element 202 are attached to sealing plate 120
with positive electrode current collecting member 600 and negative
electrode current collecting member 700 being interposed
therebetween. Thus, as shown in FIG. 10, first electrode assembly
element 201 and second electrode assembly element 202 are connected
to sealing plate 120, thereby electrically connecting electrode
assembly 200 to positive electrode terminal 400 and negative
electrode terminal 500.
[0065] (Formation of Electrode Assembly 200 and Prismatic Secondary
Battery 1)
[0066] From the state shown in FIG. 10, first electrode assembly
element 201 and second electrode assembly element 202 are stacked
on each other. On this occasion, first positive electrode tab group
211A and second positive electrode tab group 212A are curved in
different directions. First negative electrode tab group 211B and
second negative electrode tab group 212B are curved in different
directions.
[0067] First electrode assembly element 201 and second electrode
assembly element 202 can be stacked on each other by a tape or the
like. Alternatively, first electrode assembly element 201 and
second electrode assembly element 202 can be stacked on each other
by placing them in an insulating sheet formed in the form of a box
or a pouch. Further, first electrode assembly element 201 and
second electrode assembly element 202 can be fixed by adhesion.
[0068] First electrode assembly element 201 and second electrode
assembly element 202 stacked on each other are enclosed with
insulating sheet 300 and are inserted into prismatic exterior body
110. Thereafter, sealing plate 120 is welded to prismatic exterior
body 110 to seal the opening of prismatic exterior body 110 by
sealing plate 120, thereby forming sealed battery case 100.
[0069] Thereafter, a non-aqueous electrolyte is injected into
battery case 100 through electrolyte solution injection hole 121
provided in sealing plate 120. Examples of the non-aqueous
electrolyte solution usable herein include a non-aqueous
electrolyte solution in which LiPF.sub.6 is dissolved at a
concentration of 1.2 mol/L in a non-aqueous solvent in which
ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl
carbonate (DEC) are mixed at a volume ratio (25.degree. C.) of
30:30:40.
[0070] After injecting the non-aqueous electrolyte, electrolyte
solution injection hole 121 is sealed by sealing member 122. By
performing the above steps, prismatic secondary battery 1 is
completed.
[0071] (Arrangement of Bus Bars 2 in Battery Pack)
[0072] FIG. 11 is a diagram showing an arrangement of bus bars in a
battery pack. In the example shown in FIG. 11, a plurality of
prismatic secondary batteries 1 are connected in series. That is,
in the example of FIG. 11, positive electrode terminals 400 and
negative electrode terminals 500 of adjacent prismatic secondary
batteries 1 are electrically connected by bus bars 2. Positive
electrode terminals 400 and negative electrode terminals 500 are
typically joined to bus bars 2 by welding.
[0073] (Joining of Electrode Terminal to Current Collecting Member
by Swaging)
[0074] FIG. 12 is a diagram showing positive electrode terminal 400
(terminal member) and first positive electrode current collector
610 (current collector) before joining by swaging, and FIG. 13 is a
diagram showing positive electrode terminal 400 (terminal member)
and first positive electrode current collector 610 (current
collector) after the joining by swaging. It should be noted that
swaged portion 400A of positive electrode terminal 400 to first
positive electrode current collector 610 will be illustrated in the
description below; however, the same structure can be employed for
swaged portion 500A.
[0075] As shown in FIG. 12, in a state in which positive electrode
terminal 400 is inserted in through holes 611, 631 formed in first
positive electrode current collector 610 and insulating member 630
and a tip hole portion 400.alpha. of positive electrode terminal
400 is exposed on the first positive electrode current collector
610 side, a jig 900 is disposed over tip hole portion 400.alpha. of
positive electrode terminal 400, and jig 900 is moved in a
direction of arrow DR900. Thus, as shown in FIG. 13, first positive
electrode current collector 610 and positive electrode terminal 400
are joined to each other, thereby forming swaged portion 400A
(joined portion) having a thickness T.
[0076] (Shape of Swaged Portion)
[0077] FIG. 14 shows an exemplary shape of swaged portion 400A. It
should be noted that the same shape as that of swaged portion 400A
can be employed for swaged portion 500A. Prismatic secondary
battery 1 according to the present embodiment has one feature in
the shape of swaged portion 400A (the same applies to swaged
portion 500A).
[0078] As shown in FIG. 14, swaged portion 400A includes: thick
portions 10 at each of which the thickness of positive electrode
terminal 400 is relatively thick; and thin portions 20 at each of
which the thickness of positive electrode terminal 400 is
relatively thin. Thickness T of thick portion 10 is, for example,
about more than or equal to 0.45 mm and less than or equal to 0.9
mm. In the present embodiment, thin portion 20 refers to a portion
having a thickness T thinner than that of thick portion 10 by about
10% or more.
[0079] Swaged portion 400A is composed of a metal such as aluminum
or copper. A nickel layer may be formed on a surface of swaged
portion 400A.
[0080] Swaged portion 400A is formed to have a thickness T that is
gradually decreased at a boundary between thick portion 10 and thin
portion 20. However, there may be formed a level difference to
change the thickness at the boundary between thick portion 10 and
thin portion 20.
[0081] Two thick portions 10 are formed to be separated from each
other in an upward/downward direction in FIG. 14. That is, the
plurality of thick portions 10 are formed to be separated from each
other in the Y axis direction (the short side direction of sealing
plate 120) orthogonal to the X axis direction (the long side
direction of sealing plate 120) in which positive electrode
terminal 400 and negative electrode terminal 500 are arranged side
by side. Each of thick portions 10 is located on the central axis
of swaged portion 400A, the central axis extending in the Y axis
direction. Typically, thick portion 10 has a portion at which
thickness T is maximum in swaged portion 400A; however, a portion
having a thicker thickness T than that of thick portion 10 may
exist in swaged portion 400A.
[0082] Each of thin portions 20 includes a first thin portion 20A
and a second thin portion 20B. First thin portion 20A extends in a
circumferential direction along the outer circumferential edge of
swaged portion 400A. First thin portion 20A may be joined to first
positive electrode current collector 610 by welding. Since the
thickness of first thin portion 20A is relatively thin, positional
deviation of a welding application position is less likely to
occur, thereby obtaining stable welding strength.
[0083] Second thin portion 20B is formed at a position adjacent to
thick portion 10 in the circumferential direction of swaged portion
400A. Second thin portion 20B extends in the radial direction of
swaged portion 400A. Second thin portion 20B is formed to extend
radially. Thick portions 10 and second thin portions 20B may be
alternately disposed in the circumferential direction of swaged
portion 400A.
[0084] At a portion at which each second thin portion 20B is
located, the outer circumferential edge of swaged portion 400A is
formed to be recessed toward the center of swaged portion 400A.
That is, the width of swaged portion 400A at second thin portion
20B is smaller than width L of swaged portion 400A at thick portion
10.
[0085] Swaged portion 400A includes a pair of straight portions
400A1 and a pair of curved portions 400A2 alternately along the
circumferential direction. Four second thin portions 20B of six
second thin portions 20B shown in FIG. 14 are located between
straight portions 400A1 and curved portions 400A2.
[0086] The planar shape of swaged portion 400A is not limited to
the one having straight portions 400A1 and curved portions 400A2.
For example, the planar shape of swaged portion 400A may be a
perfect circular shape or an elliptical shape.
[0087] Each of first thin portions 20A is formed by forming swaged
portion 400A of positive electrode terminal 400 to first positive
electrode current collector 610 and then pressing swaged portion
400A.
[0088] Each of second thin portions 20B is formed at the time of
the swaging step of forming swaged portion 400A of positive
electrode terminal 400 to first positive electrode current
collector 610, i.e., is formed at the same time as the formation of
swaged portion 400A. However, second thin portion 20B may be formed
by forming swaged portion 400A and then pressing swaged portion
400A.
[0089] In the example of FIG. 14, first thin portions 20A and
second thin portions 20B are formed in ranges of angles .theta.1,
.theta.2(=130.degree.) in the circumferential direction. That is,
first thin portions 20A and second thin portions 20B are formed
within a range of less than or equal to about .+-.65.degree. with
respect to the X axis direction. In this way, thick portions 10 can
be selectively provided at both ends of prismatic secondary battery
1 in the short side direction (Y axis direction) of prismatic
secondary battery 1, the both ends of prismatic secondary battery 1
requiring relatively large strength in swaged portion 400A. As a
result, strength of joining of positive electrode terminal 400 to
first positive electrode current collector 610 by swaged portion
400A can be improved without excessively increasing the size of
swaged portion 400A. As a result, stable electric conduction
between positive electrode terminal 400 and first positive
electrode current collector 610 can be achieved.
[0090] FIGS. 15 to 18 show modifications of the shape of swaged
portion 400A. As shown in FIG. 15, only radial second thin portions
20B and thick portions 10 may be provided without forming first
thin portions 20A. Further, as shown in FIG. 16, first thin
portions 20A and second thin portions 20B (not shown in FIG. 16
because the positions and shapes thereof are changed as
appropriate) may be formed in thin portion formation regions
20.beta. that are within a range of less than or equal to about
.+-.65.degree. with respect to the X axis direction. Further, as
shown in FIG. 17, only second thin portions 20B (also not shown in
FIG. 17 because the positions and shapes thereof are changed as
appropriate) may be formed in thin portion formation regions
20.beta. that are within a range of less than or equal to about
.+-.65.degree. with respect to the X axis direction. Further, as
shown in FIG. 18, second thin portions 20B may be formed only in
the vicinity of the outer circumferential edge portion of swaged
portion 400A and may not reach the inner circumferential portion of
swaged portion 400A.
[0091] (Application to Outside of Battery Case 100)
[0092] In the above-described example, swaged portion 400A inside
battery case 100 has been described; however, as shown in FIG. 19,
the same configuration can be employed for a swaged portion 400B of
a terminal member 401 of positive electrode terminal 400 to an
external terminal 402 (conductive member). That is, the structure
of joining according to the present disclosure is also applicable
to a structure of joining of a terminal member to a conductive
member, which are disposed outside battery case 100.
[0093] Although the embodiments of the present invention have been
described and illustrated in detail, it is clearly understood that
the same is by way of illustration and example only and is not to
be taken by way of limitation, the scope of the present invention
being interpreted by the terms of the appended claims.
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